DC-DC Converter Assembly with an Output Inductor Accommodating a Power Stage Attached to a Circuit Board

ABSTRACT

A DC-DC converter assembly includes a board having a first side and a second side opposite the first side, a power stage die of a DC-DC converter attached to the first side of the board, and an output inductor electrically connected to an output of the power stage die and disposed over the power stage die on the first side of the board. The output inductor includes a magnetic core and an electrical conductor having first and second terminals attached to the first side of the board. The output inductor accommodates the power stage die under the magnetic core so that the power stage die is interposed between the magnetic core and the board. A corresponding method of manufacturing the DC-DC converter assembly and method of manufacturing the output inductor are also disclosed.

TECHNICAL FIELD

The instant application relates to DC-DC converters, and moreparticularly to optimal placement of DC-DC converter components on acircuit board.

BACKGROUND

DC-DC converters include several active and passive components,including a power stage for regulating the voltage of a load such as aprocessor. The power stage is coupled to the load by an output inductor.The components of a DC-DC converter, including the output inductor, areattached to a printed circuit board (PCB) together with the load. ThePCB has various electrical pathways for electrically interconnecting thecomponents of the DC-DC converter, and electrically connecting the powerstage of the converter to the load. DC-DC converter power stages areconventionally attached to the PCB in the same plane as the outputinductor, increasing the size of the PCB. Also, conventional layoutdesign practices for PCBs further complicate such an arrangement of theDC-DC converter components.

SUMMARY

According to an embodiment of a DC-DC converter assembly, the DC-DCconverter assembly comprises a board having a first side and a secondside opposite the first side, a power stage die of a DC-DC converterattached to the first side of the board, and an output inductorelectrically connected to an output of the power stage die and disposedover the power stage die on the first side of the board. The outputinductor comprises a magnetic core and an electrical conductor havingfirst and second terminals attached to the first side of the board. Theoutput inductor accommodates the power stage die under the magnetic coreso that the power stage die is interposed between the magnetic core andthe board.

According to an embodiment of a method of manufacturing a DC-DCconverter assembly, the method comprises: attaching a power stage die ofa DC-DC converter to a first side of a board, the board further having asecond side opposite the first side; positioning an output inductor overthe power stage die on the first side of the board, the output inductorcomprising a magnetic core and an electrical conductor having first andsecond terminals, the output inductor accommodating the power stage dieunder the magnetic core so that the power stage die is interposedbetween the magnetic core and the board; and attaching the first andsecond terminals of the output inductor to the first side of the boardso that the output inductor is electrically connected to an output ofthe power stage die.

According to an embodiment of a method of manufacturing an outputinductor, the method comprises: forming first and second sections of amagnetic core, the second section having a thinner inner region and athicker outer region, the thinner inner region being thin enough toaccommodate a power stage die of a DC-DC converter positioned under thesecond section of the magnetic core without the power stage diecontacting the thinner inner region and the thicker outer region of thesecond section; placing an electrical conductor on the second section;and attaching the first section to the second section so that themagnetic core secures the electrical conductor and the electricalconductor has contactable terminals.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description, and uponviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The elements of the drawings are not necessarily to scale relative toeach other. Like reference numerals designate corresponding similarparts. The features of the various illustrated embodiments can becombined unless they exclude each other. Embodiments are depicted in thedrawings and are detailed in the description which follows.

FIG. 1, which includes FIGS. 1A through 1D, illustrates different viewsof an embodiment of an output inductor shaped to accommodate a powerstage die of a DC-DC converter.

FIG. 2, which includes FIGS. 2A and 2B, illustrates different steps of amethod of manufacturing the output inductor of FIG. 1.

FIG. 3, which includes FIGS. 3A through 3D, illustrates different viewsof another embodiment of an output inductor shaped to accommodate apower stage die of a DC-DC converter.

FIG. 4, which includes FIGS. 4A through 4D, illustrates different viewsof yet another embodiment of an output inductor shaped to accommodate apower stage die of a DC-DC converter.

FIG. 5 illustrates a side view of still another embodiment of an outputinductor shaped to accommodate a power stage die of a DC-DC converter.

FIG. 6 illustrates a top plan view of an embodiment of a DC-DC converterassembly with output inductors shaped to accommodate power stage dies ofa DC-DC converter.

FIG. 7 illustrates an enlarged view of FIG. 6.

FIG. 8 illustrates a bottom plan view of the DC-DC converter assembly ofFIG. 6.

DETAILED DESCRIPTION

According to embodiments described herein, each power stage die of aDC-DC converter is placed under the corresponding output inductor forthat power stage e.g. in a buck topology in order to reduce the overallsize of the DC-DC converter solution. Each power stage provides anoutput phase of the converter to a load. In the case of a single-phaseDC-DC converter, a single power stage is provided. In the case of amulti-phase DC-DC converter, a power stage is provided for each phase ofthe converter. Each power stage die delivers a phase current through anoutput inductor to the load regulated by the DC-DC converter. Each powerstage die can have a high-side transistor and a low-side transistor forcoupling to the load through the corresponding output inductor. Thehigh-side transistor of each power stage switchably connects the load toan input voltage of the DC-DC converter and the corresponding low-sidetransistor switchably connects the load to ground at different periods.Each power stage die can include active semiconductor components such asMOSFETs (metal oxide semiconductor field effect transistors), drivers,etc. and corresponding passive components. The passive components can beexcluded from the die and provided as separate components. In each case,the power stage die includes at least the active semiconductorcomponents needed to provide an output phase of the DC-DC converter tothe load and is placed under the corresponding output inductor whenattached to a board such as a PCB to form a DC-DC converter assembly.

FIG. 1, which includes FIGS. 1A through 1D, illustrates different viewsof an output inductor 100 shaped to accommodate a power stage die of aDC-DC converter under the inductor 100. FIG. 1A shows an angledperspective of the output inductor 100, FIG. 1B shows a side view of theoutput inductor 100, FIG. 1C shows a front view of the output inductor100, and FIG. 1D shows a bottom view of the output inductor 100.

The output inductor 100 comprises a magnetic core 102 and an electricalconductor 104 having first and second terminals 106, 108 for attachingto a board such as a PCB. The electrical conductor 104 can be shaped asa staple, for example. Regardless, the magnetic core 102 has a cutout110 having a width (F) and length (L) to accommodate i.e. provide roomfor the power stage die. In addition, the terminals 104, 106 are spacedapart at opposing sides of the magnetic core 102 so that the power stagedie fits between the terminals 104, 106. This way, the power stage diecan be interposed between the magnetic core 102 and the board when theoutput inductor 100 and power stage die are attached to the same side ofthe board. The power stage die and board are not shown in FIG. 1 forease of illustration.

According to this embodiment, the output inductor 100 is manufactured byforming first and second sections 112, 114 of the magnetic core 102. Thesecond section 114 has a thinner inner region (T1) and a thicker outerregion (T2). The thinner inner region T1 is thin enough to accommodate apower stage die of a DC-DC converter positioned under the second section114 of the magnetic core 102 without the power stage die contacting thethinner inner region T1 and the thicker outer region T2 of the secondsection 114. The electrical conductor 104 of the output inductor 100 isplaced on the second section 114 e.g. by sliding the conductor 104 inplace over the second section 114. The thicker outer region T2 of thesecond section 114 has a width (E) along opposing sides of the thickerouter region T2. The terminals 106, 108 of the electrical conductor 104have a width (D) and can be seated in notches formed in the opposingsides of the thicker outer region T2 of the second section 114.

The first section 112 is then attached to the second section 114 e.g. byan adhesive so that the magnetic core 102 secures the electricalconductor 104 and the terminals 106, 108 of the conductor 104 arecontactable. In one embodiment, the second section 114 of the magneticcore 102 is formed by molding a magnetic material in a mold shaped toform the thinner inner region T1 and the thicker outer region T2 of thesecond section 114. Regardless, the magnetic core 102 has a totalthickness (C) measured along the first section 112 and the thicker outerregion T2 of the second section 114. The gap (G) between the thinnerinner region T1 and the thicker outer region T2 of the second section114 is sufficient to accommodate a power stage die of a DC-DC converterplaced under the magnetic core 102 of the output inductor 100.

FIG. 2, which includes FIGS. 2A and 2B, illustrates different steps inan alternate method of manufacturing the output inductor 100 of FIG. 1.Instead of sliding the electrical conductor 104 into place on the secondsection 114 of the magnetic core 102, the electrical conductor 104 isshaped around the second section 114 as shown in FIG. 2A. According tothis embodiment, the electrical conductor 104 has a planar top portion120 placed on the top side of the second section 114 and legs 122 thatare bent outward. After the planar top portion 120 of the conductor 104is placed on the top side of the second section 114, the legs 122 arebent inward into contact with the corresponding sides of the secondsection 114 of the magnetic core 102 as indicated by the laterallyinward facing arrows in FIG. 2A. The first section 112 is then attachedto the second section 114 as indicated by the downward facing arrow inFIG. 2A. The resulting output inductor 100 with gap (G) foraccommodating a power stage die of a DC-DC converter is shown in FIG.2B.

FIG. 3, which includes FIGS. 3A through 3D, illustrates different viewsof another embodiment of the output inductor 100. FIG. 3A shows a frontside view of the output inductor 100, FIG. 3B shows a front side view ofthe output inductor 100 with a power stage die 200 of a DC-DC converterplaced under the magnetic core 102 of the inductor 100, FIG. 3C shows abottom view of the output inductor 100, and FIG. 3D shows a bottom viewof the output inductor 100 with the power stage die 200 in place. Thethickness of the power stage die 200 is labeled ‘Tdie’ and the gap inthe magnetic core 102 which accommodates the power stage die 200 islabeled ‘G’ in FIG. 3B. The embodiment shown in FIG. 3 is similar to theembodiment shown in FIG. 1, however, the thicker outer region T2 of thesecond section 114 of the magnetic core 102 comprises a single post 202at two ends which act as a stop for the electrical conductor 104 whilebeing slid into place on the second section 114 in the directionindicated by the downward facings arrows in FIG. 3C. In one embodiment,the second section 114 of the magnetic core 102 is formed by molding amagnetic material in a mold shaped to yield the posts 202 at two ends ofthe second section 114.

FIG. 4, which includes FIGS. 4A through 4D, illustrates different viewsof yet another embodiment of an output inductor 300 shaped toaccommodate a power stage die of a DC-DC converter under the outputinductor 300. FIG. 4A shows an angled perspective of the output inductor300, FIG. 4B shows a side view of the output inductor 300, FIG. 4C showsa front view of the output inductor 300, and FIG. 4D shows a bottom viewof the output inductor 300. The embodiment shown in FIG. 4 is similar tothe embodiment shown in FIG. 1, however, the second section 114 of themagnetic core 102 has a uniform thickness and therefore the bottom side115 of the second section 114 is planar according to this embodiment.The terminals 106, 108 of the output inductor 300 extend from aperiphery of the magnetic core 102 beyond the planar bottom side 115 ofthe second section 114 by a distance corresponding to at least thethickness of the power stage die to realize a gap (G) between the planarside 115 of the magnetic core 102 and the board to which the componentsare to be mounted. The gap realized by the extended terminals 106, 108is sufficient to accommodate the power stage die under the magnetic core102. The terminals 106, 108 of the output inductor 300 can be attachedto the same side of the board as the power stage die. Alternatively, theterminals 106, 108 can be rounded leads which pass through the board andare soldered on the other side of the board. In each case, the powerstage die and board are not shown in FIG. 4 for ease of illustration.

FIG. 5 illustrates a side view of still another embodiment of an outputinductor 400 shaped to accommodate a power stage die of a DC-DCconverter under the output inductor 400. The embodiment shown in FIG. 5is similar to the embodiment shown in FIG. 4, however, the terminals106, 108 are generally coplanar with the bottom side 115 of the magneticcore 102. The height extension for accommodating the power stage dieunder the magnetic core 102 is provided by blocks 402 such as standoffswhich are attached to each of the terminals 106, 108 at the periphery ofthe magnetic core 102. The blocks 402 each have a thicknesscorresponding to at least a thickness of the power stage die, to realizea gap (G) between the magnetic core 102 and the board to which thecomponents are to be attached. The gap realized by the blocks 402 issufficient to accommodate the power stage die under the magnetic core.The power stage die and board are not shown in FIG. 5 for ease ofillustration.

FIG. 6 illustrates a plan view of a first side 501 of a PCB 500 to whicha plurality of power stage dies 502 of a DC-DC converter are attached.In this case, the DC-DC converter is a multi-phase converter and each ofthe power stage dies 502 delivers a phase current through an outputinductor 504 to a load 506 regulated by the DC-DC converter. FIG. 6illustrates the DC-DC converter assembly prior to attachment of theoutput inductors 504 to the PCB 500. The load 506 is attached to thesame side 501 of the PCB 500 as the power stage dies 502, and can be anytype of circuit requiring a regulated voltage such as one or moreprocessors. Also attached to the first side 501 of the PCB 500 are inputcapacitors 508 that provide the shortest current commutation loop forthe respective power stage dies 502. In one embodiment, these inputcapacitors 508 are also accommodated under the output inductors 504.According to this embodiment, the power stage dies 502 and the inputcapacitors 508 attached to the first side 501 of the PCB 500 areinterposed between the magnetic core of the corresponding outputinductor 504 and the PCB 500 after attachment to the first side 501 ofthe PCB 500. In other embodiments, these input capacitors 508 are notaccommodated under the output inductors 504. In either case, the inputcapacitors 508 attached to the first side 501 of the PCB 500 areelectrically connected to input terminals of the corresponding powerstage die 502 e.g. by electrically conductive vias and/or traces whichare part of the PCB 500.

FIG. 7 illustrates an enlarged view of FIG. 6, after output inductors504 shaped to accommodate the power stage dies 502 under the outputinductors 504 are attached to the first side 501 of the PCB 500 over therespective power stage dies 502. Each of the output inductors 504comprises a magnetic core and an electrical conductor having first andsecond terminals e.g. according to any of the inductor embodimentspreviously described herein. The terminals of each output inductor 504are attached to electrically conductive contact regions 510 at the firstside 501 of the PCB 500, electrically connecting the respective outputinductors 504 to the output of the corresponding power stage die 502e.g. by electrically conductive vias and/or traces of the PCB 500connected to the contact regions 510. Each output inductor 504accommodates the power stage die 502 under the magnetic core of thatinductor 504 so that the power stage die 502 is interposed between themagnetic core and the PCB 500.

In one embodiment, the magnetic core of each output inductor 504 has athinner inner region and a thicker outer region so that a gap existsbetween the thinner inner region and the first side 501 of the board 500for accommodating the thickness of the corresponding power stage die 502e.g. according to any of the embodiments illustrated in FIGS. 1 through3. In another embodiment, the magnetic core of each output inductor 504has a planar side facing the first side 501 of the board 500 and theterminals of the output inductor 504 extend from a periphery of themagnetic core beyond the planar side by a distance corresponding to atleast the thickness of the corresponding power stage die 502 to realizea gap between the planar side of the magnetic core and the first side501 of the PCB 500 that accommodates the power stage die 502 e.g.according to the embodiment illustrated in FIG. 4. In yet anotherembodiment, the terminals of each output inductor 504 are attached tothe first side 501 of the PCB 500 by a set of blocks at a periphery ofthe magnetic core and each block has a thickness corresponding to atleast the thickness of the corresponding power stage die 502 to realizea gap between the magnetic core and the first side 501 of the PCB 500that accommodates the power stage die 502 e.g. according to theembodiment illustrated in FIG. 5. In each case the power stage dies 502fit under the corresponding output inductor 504. In some cases theoutput inductors 504 completely cover the respective power stage dies502 as shown in FIG. 7.

Each magnetic core of the output inductors 504 can contact or be spacedapart from the underlying power stage die 502. In one embodiment, thethickness (Tdie) of the power stage die 502 and the gap (G) between thethinner inner region and the first side 501 of the PCB 500 are both lessthan 1 mm (FIG. 3B illustrates an embodiment of the power stage diethickness ‘Tdie’ and the gap ‘G’ for accommodating the die under theinductor).

Less PCB surface area is needed when the power stage dies 502 are atleast partly accommodated under the corresponding output inductors 504as described herein, and therefore the size of the PCB 500 can bereduced correspondingly. The stacked inductor/power stage diearrangements described herein are also particularly advantageous forpower stage dies 502 that dissipate low power and therefore do notrequire a dedicated heat sink on the side of the power stage die 502facing the corresponding output inductor 504. In one embodiment, eachpower stage die 502 such as Infineon part number DrBlade TDA21320dissipates less than 2 W at a thermal design current (TDC) of the DC-DCconverter. TDC is the sustained (DC equivalent) current that the load(e.g. processor) is capable of drawing indefinitely and defines thecurrent to use for worst-case voltage regulator temperature assessment.At TDC, voltage regulator components (such as switching transistors andinductors) reach maximum temperature and may heat the PCB layers andneighboring components above their thermal limits. Actual component andboard temperatures are established by the envelope of system operatingconditions. This includes but is not limited to the DC-DC converterlayout, load fan selection, ambient temperature, chassis configuration,etc.

FIG. 8 illustrates a plan view of a second side 503 of the PCB 500. Thesecond side 503 is opposite the first side 501 shown in FIGS. 6 and 7.Input capacitors 512 other than the ones providing the shortest currentcommutation loop for the power stage dies 502 are attached to the secondside 503 of the PCB 500. Also attached to the second side 503 of the PCB500 are output capacitors 514 electrically connected between therespective output inductors 504 and the load 506. Decoupling capacitors516 electrically connected to the power terminals of the power stagedies 502 are also attached to the second side 503 of the PCB 500.Additional passive components electrically connected to the power stagedies 502 can also be attached to the second side 503 of the PCB 500 suchas boot capacitors 518, capacitors 520 for current monitoring circuits,etc. At least some of these capacitors 512, 514, 516, 518, 520 can bedisposed on the second side 503 of the PCB 500 at least partly withinthe footprint of the corresponding output inductor 504 attached to thefirst side 501 of the PCB 500. The footprint of one of the outputinductors 504 is indicated by a dashed box in FIG. 8. The quantity andtype of passive components attached to the second side 503 of the PCB500 depend on the type of power stage dies 502 and DC-DC converter. Inone embodiment, the footprint of the components of the DC-DC convertersystem is at least half or at least a third of the size as the combinedsurface area of the individual components.

Spatially relative terms such as “under”, “below”, “lower”, “over”,“upper” and the like, are used for ease of description to explain thepositioning of one element relative to a second element. These terms areintended to encompass different orientations of the device in additionto different orientations than those depicted in the figures. Further,terms such as “first”, “second”, and the like, are also used to describevarious elements, regions, sections, etc. and are also not intended tobe limiting. Like terms refer to like elements throughout thedescription.

As used herein, the terms “having”, “containing”, “including”,“comprising” and the like are open-ended terms that indicate thepresence of stated elements or features, but do not preclude additionalelements or features. The articles “a”, “an” and “the” are intended toinclude the plural as well as the singular, unless the context clearlyindicates otherwise.

With the above range of variations and applications in mind, it shouldbe understood that the present invention is not limited by the foregoingdescription, nor is it limited by the accompanying drawings. Instead,the present invention is limited only by the following claims and theirlegal equivalents.

What is claimed is:
 1. A DC-DC converter assembly, comprising: a boardhaving a first side and a second side opposite the first side; a powerstage die of a DC-DC converter attached to the first side of the board;and an output inductor electrically connected to an output of the powerstage die and disposed over the power stage die on the first side of theboard, the output inductor comprising a magnetic core and an electricalconductor having first and second terminals attached to the first sideof the board, the output inductor accommodating the power stage dieunder the magnetic core so that the power stage die is interposedbetween the magnetic core and the board.
 2. The DC-DC converter assemblyof claim 1, wherein the magnetic core is spaced apart from the powerstage die.
 3. The DC-DC converter assembly of claim 1, wherein themagnetic core has a thinner inner region and a thicker outer region sothat a gap exists between the thinner inner region and the first side ofthe board, and wherein the gap accommodates a thickness of the powerstage die.
 4. The DC-DC converter assembly of claim 3, wherein thethickness of the power stage die and the gap between the thinner innerregion and the first side of the board are both less than 1 mm.
 5. TheDC-DC converter assembly of claim 1, wherein the magnetic core has aplanar side facing the first side of the board, and wherein the firstand second terminals of the output inductor extend from a periphery ofthe magnetic core beyond the planar side by a distance corresponding toat least a thickness of the power stage die to realize a gap between theplanar side of the magnetic core and the board that accommodates thepower stage die.
 6. The DC-DC converter assembly of claim 1, wherein thefirst and second terminals of the magnetic core are attached to thefirst side of the board by first and second blocks at a periphery of themagnetic core, and wherein the first and second blocks each have athickness corresponding to at least a thickness of the power stage dieto realize a gap between the magnetic core and the board thataccommodates the power stage die.
 7. The DC-DC converter assembly ofclaim 1, wherein the DC-DC converter is a multi-phase converter and thepower stage die provides one phase of the multi-phase converter.
 8. TheDC-DC converter assembly of claim 1, wherein the power stage diedissipates less than 2 W at a thermal design current of the DC-DCconverter.
 9. The DC-DC converter assembly of claim 1, furthercomprising: a load attached to the first side of the board; a pluralityof input capacitors electrically connected to input terminals of thepower stage die, the input capacitors that provide a shortest currentcommutation loop for the power stage die being attached to the firstside of the board and the other input capacitors being attached to thesecond side of the board; an output capacitor electrically connectedbetween the output inductor and the load, and attached to the secondside of the board; and a plurality of decoupling capacitors electricallyconnected to power terminals of the power stage die, and attached to thesecond side of the board.
 10. The DC-DC converter assembly of claim 9,wherein the output inductor accommodates the input capacitors attachedto the first side of the board under the magnetic core so that the powerstage die and the input capacitors attached to the first side of theboard are interposed between the magnetic core and the board afterattachment to the first side of the board.
 11. The DC-DC converterassembly of claim 9, wherein at least some of the capacitors attached tothe second side of the board are disposed at least partly within afootprint of the output inductor attached to the first side of theboard.
 12. The DC-DC converter assembly of claim 1, wherein theelectrical conductor is shaped like a staple and the terminals arespaced apart at opposing sides of the magnetic core so that power stagedie fits between the terminals.
 13. The DC-DC converter assembly ofclaim 1, wherein the output inductor completely covers the power stagedie.
 14. A method of manufacturing a DC-DC converter assembly, themethod comprising: attaching a power stage die of a DC-DC converter to afirst side of a board, the board further having a second side oppositethe first side; positioning an output inductor over the power stage dieon the first side of the board, the output inductor comprising amagnetic core and an electrical conductor having first and secondterminals, the output inductor accommodating the power stage die underthe magnetic core so that the power stage die is interposed between themagnetic core and the board; and attaching the first and secondterminals of the output inductor to the first side of the board so thatthe output inductor is electrically connected to an output of the powerstage die.
 15. The method of claim 14, wherein the magnetic core has athinner inner region and a thicker outer region so that a gap existsbetween the thinner inner region and the first side of the board, andwherein the gap accommodates a thickness of the power stage die.
 16. Themethod of claim 14, wherein the magnetic core has a planar side facingthe first side of the board, and wherein the first and second terminalsof the output inductor extend from a periphery of the magnetic corebeyond the planar side by a distance corresponding to at least athickness of the power stage die to realize a gap between the planarside of the magnetic core and the board that accommodates the powerstage die.
 17. The method of claim 14, comprising attaching the firstand second terminals of the output inductor to the first side of theboard by first and second blocks at a periphery of the magnetic core,and the first and second blocks each having a thickness corresponding toat least a thickness of the power stage die to realize a gap between themagnetic core and the board that accommodates the power stage die. 18.The method of claim 14, wherein the DC-DC converter is a multi-phaseconverter and the power stage die provides one phase of the multi-phaseconverter.
 19. The method of claim 14, wherein the power stage diedissipates less than 2 W at a thermal design current of the DC-DCconverter.
 20. The method of claim 14, further comprising: attaching aload to the first side of the board; attaching input capacitors thatprovide a shortest current commutation loop for the power stage die tothe first side of the board, the input capacitors being electricallyconnected to input terminals of the power stage die; attachingadditional input capacitors to the second side of the board, theadditional input capacitors being electrically connected to the inputterminals of the power stage die; attaching an output capacitor to thesecond side of the board, the output capacitor being electricallyconnected between the output inductor and the load; and attaching aplurality of decoupling capacitors to the second side of the board, thedecoupling capacitors being electrically connected to power terminals ofthe power stage die.
 21. The method of claim 20, wherein the outputinductor accommodates the input capacitors attached to the first side ofthe board under the magnetic core so that the power stage die and theinput capacitors attached to the first side of the board are interposedbetween the magnetic core and the board after attachment to the firstside of the board.
 22. A method of manufacturing an output inductor, themethod comprising: forming first and second sections of a magnetic core,the second section having a thinner inner region and a thicker outerregion, the thinner inner region being thin enough to accommodate apower stage die of a DC-DC converter positioned under the second sectionof the magnetic core without the power stage die contacting the thinnerinner region and the thicker outer region of the second section; placingan electrical conductor on the second section; and attaching the firstsection to the second section so that the magnetic core secures theelectrical conductor and the electrical conductor has contactableterminals.
 23. The method of claim 22, wherein forming the secondsection of the magnetic core comprises molding a magnetic material in amold shaped to form the thinner inner region and the thicker outerregion of the second section.